bjr
a = -2/3 et b = -4/7
• 3a
3 x (-2/3) = -(3 x 2) /3 on simplifie par 3
= -2
• a : b
(-2/3) /(-4/7) = (2/3)/ (4/7) (signe +)
= (2/3) x (7/4) (on multiplie par l'inverse)
= (2 x 7)/(3 x 4) (on simplifie par 2)
= (1 x 7)/(3 x 2)
=7/6
• a + (5/2)b
( -2/3) + (5/2)(-4/7) = (-2/3) - (5 x 4)/(2 x 7) on simplifie par 2
= (-2/3) - (5 x 2)/(1 x 7)
= -(2/3) - (10/7) dénominateur commun 21
= -(2 x 7)/21 - (10 x 3) 21
= -14/21 - 30 / 21
= -44/21
